Polishing pad for wafer polishing apparatus

ABSTRACT

A polishing pad for a wafer polishing apparatus according to an embodiment includes: a first NAP layer having an upper surface in direct contact with a wafer; a second NAP layer disposed under the first NAP layer to support the first NAP layer; and a polyethylene terephthalate film (PET film) layer disposed under the second NAP layer to be attached to a surface plate.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2018-0106324 filed in Korea on Sep. 6, 2018 which is hereby incorporated in its entirety by reference as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to a polishing pad of a wafer polishing apparatus, and more particularly, to a polishing pad capable of decreasing compressibility and increasing hardness.

BACKGROUND

Generally, in a polishing pad of a wafer polishing apparatus, as a use time of the polishing pad is increased, a thickness of the polishing pad is decreased, and a pressure applied to a wafer by a polishing head is kept constant, so that the wafer is polished in a state in which the thickness of the polishing pad is thinner than that in the former half of a use of the polishing pad. Accordingly, an exposed region not in contact with the polishing pad in an edge region of the wafer is increased, and thus there is a problem that edge roll-off is increased.

SUMMARY

Accordingly, the present invention is directed to providing a polishing pad for a wafer polishing apparatus capable of controlling an increase of edge roll-off due to a change-with-time of the polishing pad during performing a wafer polishing process and intermittent uneven wear generated during polishing, and a manufacturing method thereof.

The present invention provides a polishing pad for a wafer polishing apparatus including a first NAP layer having an upper surface in direct contact with a wafer, a second NAP layer disposed under the first NAP layer to support the first NAP layer, and a polyethylene terephthalate film (PET film) layer disposed under the second NAP layer to be attached to a surface plate.

According to an embodiment, a compressibility of the first NAP layer may be 12% or less.

According to an embodiment, a hardness of the first NAP layer may be 22° or more.

According to an embodiment, a compressibility of the second NAP layer may be 10% to 30%.

According to an embodiment, an elastic modulus of the second NAP layer may be 95% or more.

According to an embodiment, a hardness of the second NAP layer may be 19° to 26°.

According to an embodiment, thicknesses of the first and second NAP layers may be 0.30 to 0.40 mm, respectively.

According to an embodiment, a thickness of the PET film layer may be 0.10 to 0.30 mm.

According to an embodiment, the first and second NAP layers may be a suede material including polyurethane.

According to an embodiment, an adhesive layer for combining the first NAP layer and the second NAP layer may be further included.

The aspects of the present invention are only a part of the preferred embodiments of the present invention, and various embodiments reflecting technical features of the present invention may be derived and understood based on the detailed description of the present invention described below by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, accompanying drawings are included to help in understanding of the present invention, and provide embodiments of the present invention with detailed description. However, technical features of the present invention are not limited to the specific drawings, and the features disclosed in the drawings may be combined with each other to constitute a new embodiment.

FIG. 1 is a view showing a first polishing pad according to a polishing apparatus of the present invention.

FIG. 2 is a view showing a removal amount profile of a first polishing pad when the elastic modulus of a pad substrate layer is increased in the first polishing pad of the present invention.

FIG. 3 is a view showing a removal amount profile of a first polishing pad when the compressibility of a pad substrate layer in the first polishing pad of the present invention is decreased and the hardness thereof is increased.

FIG. 4 is a view showing a removal amount profile of a first polishing pad when the compressibility of a pad surface layer in the first polishing pad of the present invention is decreased and the hardness thereof is increased.

FIG. 5 is a view showing a second polishing pad according to a second polishing apparatus of the present invention.

FIG. 6 is a view showing a change in a pad thickness according to an increase in a use time of a second polishing pad of the present invention.

FIG. 7 is a view comparing ESFQD MEANs of first and second polishing pads according to a polishing apparatus of the present invention.

FIG. 8 is a view showing a removal amount profile according to a second polishing pad of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the present invention will be described in detail with reference to the exemplary embodiments, and will be explained in detail with reference to the accompanying drawings in order to help in understanding of the invention.

However, embodiments according to one embodiment of the present invention may be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the embodiments to be described below. The embodiments of the present invention are provided to more fully explain the invention for those skilled in the art.

In addition, relational terms such as “first” and “second”, “upper portion” and “lower portion”, etc. used below, without necessarily requiring or enclosing any physical or logical relationship or order between its entities or elements, may be used only to distinguish one entity or element from another entity or element.

FIG. 1 is a view showing a first polishing pad according to a polishing apparatus of the present invention.

A first polishing pad 100 according to a polishing apparatus may include a NAP layer 110 and a nonwoven fabric layer 120.

The NAP layer 110 forms an upper layer of the first polishing pad 100, and may perform polishing while being in contact with a wafer. The NAP layer 110 may be referred to as a pad surface layer of the first polishing pad 100. The NAP layer 110 may be composed of a suede material including polyurethane. At this time, the NAP layer 110 may include a suede material having a predetermined hardness or more.

The nonwoven fabric layer 120 may be disposed under the NAP layer 110 described above. The nonwoven fabric layer 120 may be referred to as a pad substrate layer of the first polishing pad 100. The nonwoven fabric layer 120 may be combined with the NAP layer 110 to support the NAP layer 110 so that the NAP layer 110 functions stably.

FIG. 2 is a view showing a removal amount profile of a first polishing pad when the elastic modulus of a pad substrate layer is increased in the first polishing pad of the present invention.

The configuration of the nonwoven fabric layer 120 for improving the elastic modulus in the first polishing pad 100 may be as shown in Table 1 below.

TABLE 1 NW (nonwoven fabric layer) (substrate) Comparative Comparative Comparative Items Example 1 Example 2 Example 3 Thickness (mm) 1.05 1 1.04 Density (g/cm³) 0.38 0.29 0.29 Compressibility (%) 13 16 14 Elasticity (%) 83 87 93 Hardness (°) 44 42 43

Referring to Table 1, the numerical value of the elastic modulus of the nonwoven fabric layer 120 may be 83% in Comparative Example 1, the numerical value of the elastic modulus of the nonwoven fabric layer 120 may be 87% in Comparative Example 2, and the numerical value of the elastic modulus of the nonwoven fabric layer 120 may be 93% in Comparative Example 3. Referring to FIG. 2, in the removal amount profile of the first polishing pad 100 according to Comparative Examples 1 to 3, the vertical axis shows the direction in which a removal amount increases according to the polishing pad, and the horizontal axis shows a diameter of a wafer.

According to a use time of the first polishing pad 100 according to Comparative Example 1, a step of an edge region in a former half of the use time of the first polishing pad 100 is 10 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 35 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 according to Comparative Example 1 may be 25 nm.

According to a use time of the first polishing pad 100 according to Comparative Example 2, a step of an edge region in a former half of the use time of the first polishing pad 100 is 9 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 29 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 according to Comparative Example 2 may be 20 nm.

According to a use time of the first polishing pad 100 according to Comparative Example 3, a step of an edge region in a former half of the use time of the first polishing pad 100 is 8 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 26 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 18 nm.

When the elastic modulus of the nonwoven fabric layer 120 according to the first polishing pad 100 increases, the recoverability of the thickness of the first polishing pad 100 increases, and as the elastic modulus of the nonwoven fabric layer 120 increases, there is an effect that a change in a removal amount in the edge region is smaller in the latter half of the use time of the first polishing pad 100 than in the former half of the use time thereof.

Accordingly, when the elastic modulus of the nonwoven fabric layer 120 increases in the first polishing pad 100, a removal amount with respect to the diametrical direction of the wafer is decreased as toward the edge region thereof from a center region of the wafer, and thus an effect of improving edge roll-off in the latter half of the use time of the polishing pad may be obtained.

FIG. 3 is a view showing a removal amount profile of a first polishing pad when the compressibility of a pad substrate layer in a first polishing pad of the present invention is decreased and the hardness thereof is increased.

In the removal amount profiles of the first polishing pads 100 according to Comparative Examples 1, 4, and 5, the vertical axis shows a direction in which a removal amount increases according to the polishing pad 100, and the horizontal axis shows a diameter of a wafer.

In the first polishing pad 100, the configuration of the nonwoven fabric layer 120 for decreasing the compressibility and increasing the hardness may be as shown in Table 2 below.

TABLE 2 NW (nonwoven fabric layer) (substrate) Comparative Comparative Comparative Items Example 1 Example 4 Example 5 Thickness (mm) 1.05 1 1.04 Density (g/cm³) 0.38 0.32 0.29 Compressibility (%) 13 10 6.5 Elasticity (%) 83 81 91 Hardness (°) 44 48 53

Referring to Table 2, the numerical value of the compressibility of the nonwoven fabric layer 120 may be 13% and the numerical value of the hardness of the nonwoven fabric layer 120 may be 44° in Comparative Example 1. The numerical value of the compressibility of the nonwoven fabric layer 120 may be 10% and the numerical value of the hardness of the nonwoven fabric layer 120 may be 48° in Comparative Example 4. The numerical value of the compressibility of the nonwoven fabric layer 120 may be 6.5% and the numerical value of the hardness of the nonwoven fabric layer 120 may be 53° in Comparative Example 5. Referring to FIG. 3, in the removal amount profiles of the first polishing pads 100 according to Comparative Examples 1, 4, and 5, the vertical axis shows a direction in which a removal amount increases according to the polishing pad 100, and the horizontal axis shows a diameter of a wafer.

According to a use time of the first polishing pad 100 according to Comparative Example 1, a step of an edge region in a former half of the use time of the first polishing pad 100 is 10 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 35 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 25 nm.

According to Comparative Example 4, a step of an edge region in a former half of a use time of the first polishing pad 100 is 10 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 27 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 17 nm.

Referring to a first removal profile 310 of Comparative Example 5, a step of an edge region in a former half of a use time of the first polishing pad 100 is 8 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 21 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 13 nm.

Accordingly, when the compressibility of the nonwoven fabric layer 120 according to the first polishing pad 100 is decreased and the hardness thereof is increased, there is an effect that a change in a removal profile is smaller in the latter half of the use time of the first polishing pad 100 than in the former half of the use time thereof.

However, referring to a second removal profile 320 of Comparative Example 5, intermittent uneven wear may be generated by increasing of a difference between a removal amount of one side surface of a wafer and a removal amount of an opposite region of the wafer due to a decrease in the compressibility and/or an increase in hardness of the nonwoven fabric layer 120. That is, a slurry supply is adversely affected when the compressibility of the nonwoven fabric layer 120 is decreased and the hardness thereof is increased, so that uneven wear may be generated in the first polishing pad 100.

Accordingly, when the compressibility of the nonwoven fabric layer 120 is decreased and the hardness thereof is increased in the first polishing pad 100, a change in a removal amount in the edge region is smaller in the latter half of the use time of the first polishing pad 100 than in the former half of the use time thereof, but uneven wear is generated in the edge region for uniform polishing of the wafer, and thus an effect of improving edge roll-off is decreased.

FIG. 4 is a view showing a removal amount profile of a first polishing pad when the compressibility of a pad surface layer in the first polishing pad of the present invention is decreased and the hardness thereof is increased.

In the first polishing pad 100, the configuration for decreasing the compressibility of the NAP layer 110 and increasing the hardness thereof may be as shown in Table 3 below.

TABLE 3 NAP (polyurethane) layer Comparative Comparative Comparative Items Example 1 Example 6 Example 7 Thickness (mm) 0.39 0.39 0.39 Density (g/cm³) 0.19 0.21 0.25 Compressibility (%) 31.5 26.5 12 Elasticity (%) 95 93 95 Hardness (°) 14 18 22

Referring to Table 3, the numerical value of the compressibility of the NAP layer 110 may be 31.5% and the numerical value of the hardness of the NAP layer 110 may be 14° in Comparative Example 1. The numerical value of the compressibility of the NAP layer 110 may be 26.5% and the numerical value of the hardness of the NAP layer 110 may be 18° in Comparative Example 6. The numerical value of the compressibility of the NAP layer 110 may be 12% and the numerical value of the hardness of the NAP layer 110 may be 22° in Comparative Example 7. Referring to FIG. 4, in the removal amount profile of the first polishing pad 100 shown in Comparative Examples 1, 6, and 7, the vertical axis shows a direction in which a removal amount increases according to the polishing pad, and the horizontal axis shows a diameter of a wafer.

According to Comparative Example 1, a step of an edge region is 10 nm in a former half of a use time of the first polishing pad 100, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 35 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 25 nm.

According to Comparative Example 6, a step of an edge region in a former half of a use time of the first polishing pad 100 is 6 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 19 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 7 nm.

According to Comparative Example 7, a step of an edge region in a former half of a use time of the first polishing pad 100 is 5 nm, and a step of an edge region in a latter half of the use time of the first polishing pad 100 is 17 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the first polishing pad 100 may be 12 nm.

Accordingly, when the compressibility of the NAP layer 110 according to the first polishing pad 100 is decreased and the hardness thereof is increased, a change in a removal amount in the edge region is smaller in the latter half of the use time of the first polishing pad 100 than in the former half of the use time thereof, and thus there is an effect that edge roll-off and a change-with-time are improved by improving a wear degree.

FIG. 5 is a view showing a second polishing pad according to a second polishing apparatus of the present invention.

Referring to FIG. 5, a second polishing pad 200 according to a polishing apparatus may be formed in a double NAP layer.

In the second polishing pad 200, a first NAP layer 210 may be disposed as a pad surface layer and a second NAP layer 220 may be disposed as a pad substrate layer.

The first NAP layer 210 may form an upper layer of the second polishing pad 200, and may perform polishing while being in contact with a wafer. The first NAP layer 210 may include a suede material having a predetermined hardness or more to have an excellent performance in decreasing edge roll-off and improving a wear degree. At this time, a thickness of the first NAP layer 210 may be 0.30 to 0.40 mm.

The second NAP layer 220 may be disposed under the first NAP layer 210 described above. The second NAP layer 220 may be combined with the first NAP layer 210 to support the first NAP layer 210 so that the first NAP layer 210 may function stably. In addition, the second NAP layer 220 may include a suede material having a predetermined elastic modulus or more to have an excellent performance in thickness reduction and recovery. At this time, a thickness of the second NAP layer 220 may be 0.30 to 0.40 mm.

The second polishing pad 200 may include a polyethylene terephthalate (PET) film layer 230 disposed under the second NAP layer 220 to be attached to a surface plate.

The PET film layer 230 may control warp characteristics of the pad and prevent penetration of air bubbles when the surface plate is attached. In the case of the PET film layer 230, since an amount of compression is close to 0, it is possible to suppress the occurrence of overheating and uneven wear due to polishing load by manufacturing a thickness of the PET film layer 230 to a predetermined thickness. At this time, the thickness of the PET film layer 230 may be 0.10 to 0.30 mm.

An adhesive layer 240 may be located between the first NAP layer 210 and the second NAP layer 220, and may combine the first NAP layer 210 and the second NAP layer 220. For example, the adhesive layer 240 may be an adhesive or an adhesive tape that adheres a lower surface of the first NAP layer 210 and an upper surface of the second NAP layer 220.

In the second polishing pad 200, the configuration of the first NAP layer 210 and the second NAP layer 220 for increasing the hardness and the elastic modulus may have characteristics as shown in Table 4 below.

TABLE 4 Surface Substrate (First NAP layer) (Second NAP layer) Thickness (mm) 0.39 0.39 Density (g/cm3) 0.25 0.25 Compressibility (%) 12 or less 10 to 30 Elasticity (%) 95 95 or more Hardness (°) 22 or more 19 to 26

Referring to Table 4, the numerical value of the compressibility of the first NAP layer 210 may be 12% and the numerical value of the hardness of the first NAP layer 210 may be 22° or more in the second polishing pad 200. The numerical value of the compressibility of the second NAP layer 220 may be 1 to 30%, the numerical value of the elastic modulus of the second NAP layer 220 may be 95% or more, and the numerical value of the hardness of the second NAP layer 220 may be 19 to 26° in the second polishing pad 200.

FIG. 6 is a view showing a change in a pad thickness according to an increase in a use time of a second polishing pad of the present invention.

Referring to FIG. 6, the vertical axis of a graph showing a thickness of a second polishing pad 200 shows a direction in which the thickness of the polishing pad increases, and the horizontal axis shows a direction in which the use time of the pad increases.

As the use time of the second polishing pad 200 is increased, all thicknesses of the polishing pad in a former half, a middle half, and a latter half are shown, respectively. When the thickness of the second polishing pad 200 is compared, as the use time of the second polishing pad 200 is increased, thicknesses of the first and second NAP layers 210 and 220 are decreased, and a thickness of the PET film layer 230 tends to be kept constant.

FIG. 7 is a view comparing ESFQD MEANs of first and second polishing pads according to a polishing apparatus of the present invention.

In a graph shown in FIG. 7, the vertical axis shows a direction in which Edge sector Site Frontside reference Q (Site least square plane) Derivation (ESFQD) increases, and the horizontal axis shows a direction in which a use time of the polishing pad increases.

ESFQD is an abbreviation for Edge sector Site Frontside reference Q (Site least square plane) Derivation, and may have a positive value or a negative value.

Referring to FIG. 7, a first graph 710 shows a change in ESFQD MEAN according to a first polishing pad 100, and a second graph 720 shows a change in ESFQD MEAN according to a second polishing pad 200.

The ESFQD MEAN value according to the first polishing pad 100 decreases as a use time of a pad is increased, and the ESFQD MEAN value according to the second polishing pad 200 also tends to decrease as the use time of the pad is increased.

At this time, since the decrease rate of the ESFQD MEAN value according to the second polishing pad 200 is smaller than that of the ESFQD MEAN value according to the first polishing pad 100 by an increase in the use time of the polishing pad, it is possible to show that flatness is improved in an edge region of the second polishing pad 200.

FIG. 8 is a view showing a removal amount profile according to a second polishing pad of the present invention.

Referring to FIG. 8, in the second polishing pad 200, a step of an edge region in a former half of a use time of the second polishing pad 200 is 5 nm, and a step of an edge region in a latter half of the use time of the second polishing pad 200 is 12 nm. Therefore, a degree of edge roll-off in the former half and the latter half of the use time of the second polishing pad 200 may be 7 nm.

Accordingly, as compared with the first polishing pad 100, a change in a removal profile in the latter half of the use time of the polishing pad 200 is smaller than that in the former half of the use time thereof, and thus there is an effect that edge roll-off and a change-with-time are improved by improving a wear degree.

In a polishing pad for a wafer polishing apparatus according to the present invention, since the hardness and elastic modulus of a pad surface layer in contact with a wafer are increased, and a use time of the polishing pad is increased and peeling of an edge portion does not occur, it is possible to prevent flatness of an edge region of a wafer to be polished from being lowered.

An effect which may be obtained by the present invention is not limited to the above-mentioned effects and other unmentioned effects will be clearly understood by those skilled in the art from the above descriptions.

The features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in the embodiments may be combined or modified with other embodiments by those skilled in the art to which the embodiments belong. Accordingly, it is to be understood that such combination and modification are included in the scope of the present invention.

DESCRIPTION OF REFERENCE NUMERALS 100, 200: polishing pad 110: NAP layer 120: nonwoven fabric layer 210: first NAP layer 220: second NAP layer 230: PET film layer 240: adhesive layer 

What is claimed is:
 1. A polishing pad for a wafer polishing apparatus comprising: a first NAP layer having an upper surface in direct contact with a wafer; a second NAP layer disposed under the first NAP layer to support the first NAP layer; and a polyethylene terephthalate film (PET film) layer disposed under the second NAP layer to be attached to a surface plate.
 2. The polishing pad for the wafer polishing apparatus of claim 1, wherein a compressibility of the first NAP layer is 12% or less.
 3. The polishing pad for the wafer polishing apparatus of claim 1, wherein a hardness of the first NAP layer is 22° or more.
 4. The polishing pad for the wafer polishing apparatus of claim 1, wherein a compressibility of the second NAP layer is 10% to 30%.
 5. The polishing pad for the wafer polishing apparatus of claim 1, wherein an elastic modulus of the second NAP layer is 95% or more.
 6. The polishing pad for the wafer polishing apparatus of claim 1, wherein a hardness of the second NAP layer is 19° to 26°.
 7. The polishing pad for the wafer polishing apparatus of claim 1, wherein thicknesses of the first and second NAP layers are 0.30 to 0.40 mm, respectively.
 8. The polishing pad for the wafer polishing apparatus of claim 1, wherein a thickness of the PET film layer is 0.10 to 0.30 mm.
 9. The polishing pad for the wafer polishing apparatus of claim 1, wherein the first and second NAP layers are a suede material including polyurethane.
 10. The polishing pad for the wafer polishing apparatus of claim 1, further comprising an adhesive layer for combining the first NAP layer and the second NAP layer. 